You'll find many compilers and parsers are written in C, it gives great portability across platforms and gives the best performance. Whether you write in C or C++ I'd think is more a matter of design choices for a parser and code gen tool. I'd probably go with C++ myself, but either is completely reasonable. You'll also be able to find lots of examples online in C/C++.

Also in this case while there are some compiler differences between platforms for C/C++ they are well documented and known. If you stay in the middle of the language and don't try to use fringe features of the language or a specific compiler then you won't have any issues. People that complain about portability or GCC etc are generally using language extensions of a specific platform compiler which can make portability a pain.